Test Overview
Test Methodology

This test utilizes a G-C rich PCR method with a FAM-labeled gene-specific primer designed to amplify the entire repeat region and a CGG repeat primer designed to anneal and amplify anywhere along the repeat region. Amplification is followed by analysis with capillary electrophoresis (CE). This test is run in conjunction with methylation PCR to determine methylation status of the gene promoter. Results may be confirmed by a second method such as Southern Blotting, if indicated.

Test Usage

Analysis of CGG repeats present in the FMR1 gene in a patient with clinical features consistent with Fragile X Syndrome or determination of the carrier status of a family member.

Reference Range *

Normal alleles: 5-44 CGG repeats; Intermediate (gray zone) mutations: 45-54 CGG repeats; Premutations: 55-200 CGG repeats; Full Mutation: >200 CGG repeats. Interpretative report provided.

Test Limitations

This assay can detect up to 200 CGG repeats in the FMR1 gene. Samples containing > 200 CGG repeats will be reported as "full mutation (>200 CGG repeats)".

Test Details
Days Set Up
Monday - Thursday
Analytic Time

21 days

Soft Order Code
FRXFA
MiChart Code
Fragile X DNA Analysis (MMGL)
Synonyms
  • FRXFAS
  • Fragile X Frag Analysis Shadow
  • FRXFA
  • Fragile X Mutation Detection by Fragment Analysis
  • FXPB
  • Fragile X Synd Car Det,Blood
  • FRAGILE X FRAG ANALYSIS
  • Fragile X Syndrome
  • x-linked mental retardation
  • Fragile X tremor ataxia syndrome
  • Fragile X associated premature ovarian insufficiency (FXPOI)
  • Autism / Intellectual Disability
Laboratory
MMGL
Section
MMGL Molecular Genetics
Specimen Requirements
Collection Instructions

Collect specimen in a lavender top tube. Send intact specimen within 24 hours if stored at room temperature or within 5 days if stored refrigerated. Include the patient's family history, pedigree, and ethnicity on the test requisition. Obtaining informed consent from the patient prior to genetic testing is strongly recommended. If desired, a UMHS Request and Consent for Genetic Testing form can be obtained from the MMGL Molecular Genetics Laboratory by contacting the MLabs Client Services Center at 800-862-7284 or online at https://mlabs.umich.edu/sites/default/files/2020-01/file/pci-mmgl_infor….

Lavender Top Tube
Normal Volume
5 - 10 mL EDTA whole blood
Minimum Volume
2 mL EDTA whole blood
Additional Information

The American College of Medical Genetics recommends that both a routine karotype (Chromosome Analysis, Blood, Constitutional) AND a molecular test (Fragile X Syndrome Mutation Detection) be performed. By ordering this test the clinician acknowledges that informed consent has been obtained from the patient as required by applicable state or federal laws and the ordering clinician has authorization from the patient permitting MLabs to report the test results to the ordering clinician. Test includes medical geneticist interpretation of results billed as a separate additional charge. This test is not available without interpretation.

Billing
CPT Code
81243
Fee Code
DA170
Pro Fee CPT
G0452-26
Prior Authorization
The Prior Authorization form is required for this test. Click here to download the PDF.
LOINC
21759-6
NY State Approved
No